This invention relates to improvements in top drive well drilling apparatus.
Copending U.S. Pat. No. 4,449,596 filed Aug. 3, 1982 by George I. Boyadjieff on "Drilling of Wells With Top Drive Unit", discloses a well drilling rig including a top drive unit which is connectable to the upper end of a drill string to drive it rotatively and which moves upwardly and downwardly with the string during the drilling operation, and which has associated with it pipe handling mechanism at the underside of the drilling unit for making and breaking joints between the drilling unit and the drill string and for suspending a pipe section or the entire string during handling operations. The drilling unit includes a tubular element which is threadedly connectible to the upper end of the string and through which drilling fluid is delivered downwardly to the string from a swivel at the upper end of the unit, and includes also a motor which drives the tubular element rotatively to turn the string as the well is drilled. The pipe handling mechanism preferably includes a powered torque wrench for making or breaking a threaded connection to the string, and an elevator which is suspended beneath the torque wrench and is adapted to engage an upper section of the drill string and support it when the string is disconnected from the tubular element of the drilling unit. The torque wrench and elevator of the apparatus of that prior application are both retained against rotation with the drill string during the drilling operation.